This research is in response to a request for applications for the design and feasibility assessment of a Phase III Trial Low Fat Diet in Women at Increased Risk for Breast Cancer. Our proposal is for establishment of a clinical unit for this study. The application is based on availability of a cohort of women at high risk of breast cancer through the Prevention-Detection Center at Roswell Park Memorial Institute. This population, combined with other high risk patients identified from the Department of Breast Surgery, consists of in excess of 375 individuals. Prior assessments of the receptivity of Prevention-Detection Center clientele to participation in research involving dietary interventions suggest a high level of interest. Our research plan would further identify and characterize individuals likely to participate in dietary intervention trials to the reduction of breast cancer. Our research plan also examines the dietary changes that can be achieved through an intervention directed mainly at reduction of dietary fat intake. The program and facilities we describe will be suited for participation in a multi-institutional trial. The research protocol to be employed in the feasibility portion of the investigation and in the longer term study will be the product of collaboration and protocol development carried out with the National Cancer Institute staff.